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In this paper, a structurally simple transmissive all-dielectric metamaterial absorber is designed, fabricated and measured. The unit cell consists of photosensitive resin and water, which the water layers composed of rectangle loop, rectangular block and traffic circle. It achieves over 90% absorption of electromagnetic waves in the frequency range between 11.0 and 27.3 GHz. Meanwhile, three absorption peaks are located at 12.5, 18.4, and 26.0 GHz, which the absorptive are 97.4%, 98.3%, and 98.5%, respectively. In addition, the characteristics of the designed metamaterial reveal wide-incident angle absorption and polarization-insensitive properties. The experimental sample is measured by using the free-space method, and the experimental results are verified to be in well agreement with the simulation data. Observing the distribution of electric and magnetic fields at different resonance frequencies, the physical mechanism of the absorption is attributed to strong magnetic resonance. Therefore, the proposed metamaterial has potential for widespread use in the fields of civilian and military. [ABSTRACT FROM AUTHOR]

We simulate, measure, and analyze an electromagnetically induced transparency-like (EIT-like) metamaterial with a unit cell composed of a Reuleaux triangle split-ring resonator (RT-SRR) and a Y-type strip (YS). The transparency peak of the EIT-like metamaterial is located at 12.54 GHz, and the transmission coefficient is 91%. The electric field distributions indicate that the RT-SRR plays the role of the bright mode, and the YS plays the role of the dark mode. The coupling between the bright and dark modes leads to the EIT-like phenomenon. The surface current distributions and the calculated results for the radiated power of the electric multipoles are used to analyze the physical mechanism behind the transparency peak, which can be understood in terms of the electric dipole interacting with the electric quadrupole. As the polarization angle increases, the transmission coefficient of the transparency peak decreases, indicating polarization sensitivity. When the YS is rotated around the center and the RT-SRR is kept fixed, the EIT-like phenomenon appears and disappears. Therefore, the proposed metamaterial has potential applications in detectors and switches. The experimental results are well-matched with the simulation results. [ABSTRACT FROM AUTHOR]

We present the design of a new type of irregular metamaterial structure that can achieve ultra-wideband absorption. The structure is created using 3D-printing to create a shell and contains multiple layers of water. The structure can achieve absorption levels greater than 0.9 in the 6.8–21.0 GHz range, with a relative bandwidth of 101.93%. The absorber also works in a wide range of incidence angles with different modes and is polarization insensitive. Measurement results obtained from a microwave experiment coincide well with the simulation results. The proposed metamaterial could be broadly applied in various civilian and military products in the future. [ABSTRACT FROM AUTHOR]

• Millimeter-scale Human-shaped microchannel designed based on the split-recombination principle. • Research on flow patterns and enhanced mass transfer in millimeter-scale and Human-shaped microchannels. • At high flow rates, the limitations of parallel flow on mass transfer can be overcome. • Optimizing the configuration of Human-shaped microchannels to enhance mass transfer performance. Based on the principle of splitting and recombining, this study designed and fabricated millimeter-scale Human-shaped microchannels. The research focused on investigating the flow patterns and mass transfer characteristics of liquid-liquid two-phase flow within the Human-shaped microchannels. The experiment utilized a water and n-butanol system to investigate the flow behavior of liquid-liquid two-phase in the channel with a flow rate ratio of 1. When the total volumetric flow rate increases from 120 µl/min to 2400 µl/min, the flow pattern experiences slug flow, slug-droplet flow, parallel flow and non-steady flow patterns respectively. The study investigated the impact of factors including total flow rate, feed method, angle, curvature, channel width, phase ration extraction efficiency and mass transfer coefficients. The Human-shaped channel exhibited superior mass transfer performance compared to conventional microchannels due to its advantageous configuration. The higher the included angle is, the stabler the flow pattern within the channel, resulting in a better mass transfer performance. Furthermore, the absence of curvature is more favorable for achieving higher mass transfer efficiency. In the experiments, the overall volume mass transfer coefficient ranged from 0.007 to 0.1742 s−1. This study can provide insights for the development and structural optimization of microchannels based on the split-recombine principle. [Display omitted] [ABSTRACT FROM AUTHOR]

A transmissive water-based metamaterial absorber(TWMA) is designed, simulated, and measured, which uses 3D-printing to manufacture. The TWMA uses a circular column and rectangular water layer structure and has no metal backplane. We have proved theoretically and experimentally that the TWMA has absorption rate exceeds 90% in the frequency ranging from 6.5 to 21.4 GHz. Furthermore, the TWMA is thermo-tunable when temperatures change from 10 to 60 °C and has the characteristics of wide angle incidence and polarization insensitivity. It can be applied to a variety of electromagnetic applications, such as reducing broadband scattering and collecting electromagnetic energy in a variable temperature environment. [ABSTRACT FROM AUTHOR]

In this study, a metamaterial comprising an N-type strip (NS) and a double split-ring resonator (DSRR) has been investigated, which is the first to exhibit the broadband electromagnetically induced transparency (EIT) effect and dual-band transmission-type polarization conversion under microwaves. The transmittance coefficient reaches a maximum value of 0.94 at 13.10 GHz, while the bandwidth of the transparency window is 4.96 GHz. At 9.48 GHz and 14.36 GHz, almost all the transmitted co-polarization waves are converted into cross-polarization waves at the polarization conversion ratios of 95% and 94%, respectively. The surface current distributions have been used to analyze the phenomena of EIT and transmission-type polarization conversion. The group delay value (15.35 ps) is calculated to exhibit the slow light effect at the transparency peak. It is expected that the proposed metamaterial will be beneficial for manufacturing slow-light devices and for communication applications. [ABSTRACT FROM AUTHOR]

• In the single anisotropy metasurface, the transmissive and reflective polarization converters are simultaneously achieved in different operation bands, which have not changing the characteristics of material. • The physical mechanism of transmissive polarization conversion is the magnetic resonance with the different layers of metal pattern. Moreover, the electric resonance plays the main role to generate reflective polarization conversion. This paper proposes a bifunctional linear-to linear polarization converter with a sandwich structure that enables transmissive and reflective polarization conversions in different operating bands, simultaneously. The unit cell of the converter metasurface comprises an S-shaped wire, a dielectric slab, and an S-shaped slot, where the S-shaped wire and slot have complementary structures and a 30° difference in orientation. When an x -polarized electromagnetic wave is incident on the proposed metasurface, most of the transmitted wave is y -polarized in the frequency range of 7.07 GHz to 7.46 GHz, while most of the reflected wave is y -polarized in the frequency range of 16.59 GHz to 16.91 GHz. The physical mechanism underlying these two types of polarization conversions was analyzed based on the surface current, and electric field distributions. Notably, the transmissive polarization conversion was primarily attributed to magnetic resonance, while its reflective counterpart was ascribed to electric resonance. In addition, the Jones vector and Stokes parameters were analyzed thereby elucidating the polarization characteristics of the proposed metasurface. Furthermore, simulation data demonstrated excellent agreement with the measured results of polarization conversion. The designed metasurface will promote subsequent research on bifunctional polarization converters. [ABSTRACT FROM AUTHOR]

In this study, a water-based metamaterial absorber (MMA) with ultra-wideband microwave absorption has been proposed and investigated. Using a special structural design, the absorption rate of the absorber exceeds 90% in the frequency range 5.5–27.5 GHz, and the absorber's thickness is only 5.8 mm. The angular tolerance of the MM absorber shows that the absorber works well under a wide angle of incidence. When bent, the absorber shows omnidirectional absorption characteristics and polarization insensitivity. As the proposed water MM absorber is low cost and easy to manufacture, it could be widely used in electromagnetic stealth and energy harvesting. [ABSTRACT FROM AUTHOR]

• Water-substrate. • Ultra-wideband. • Temperature insensitive. • Wide incident angle. • Polarization insensitive. The natural water has frequency dispersion and its permittivity is also related to temperature, which are important factors to design temperature insensitive absorber at microwave frequency. Here, a water-based metamaterial absorber which is fabricated by 3D-printing is proposed. The absorber can perform stably at different temperatures and it also shows 90% absorption in the frequency range of 7.9–21.7 GHz. The experiment proves that the absorber can work at a wide incident angle and is polarization insensitive. Based on these features, the water-based absorber could be applied to various electromagnetic scenarios such as stealth technology and electromagnetic compatibility in temperature-variable environment. [ABSTRACT FROM AUTHOR]

Highlight • We proposed tunable and polarization sensitive electromagnetically induced transparency metamaterial. • When incident angles vary from 0° to 60°, the transmission spectra has two transmission windows in TE mode. • In TM mode, the transmission window has broadened in the transmission spectra. • On the other hand, the proposed metamaterial has slow light effect and the largest value of group index is 30 in the transparency peak. • According to the property of the designed metamaterial, we believe it suggests the future possibility for a new type of applications in sensing and filtering device. Abstract We demonstrate a classical analogue of electromagnetically induced transparency (EIT) metamaterial that consisting of anomalous split resonance ring and cross-shaped wire with simulations and experiments. The transmission spectrum is tunable with the incident angles varies from 0° to 60° in different modes. Under normal incident wave, the metamaterial leads to polarization insensitive EIT-like effect. The distributions of surface current at peaks and dips of transmission have been analyzed. Furthermore, the group index presents maximum at the transparency peak, which verifies the slow light effect. The proposed metamaterial could provide an avenue for various applications, such as refractive index sensor and microwave switch. [ABSTRACT FROM AUTHOR]

The metasurface is a functional film device based on a subwavelength structure, which has a strong light field control ability and has the advantages of ultrathin, low loss, and easy manufacturing. However, realizing a multifunctional metasurface, yet simple enough to design, manufacture, and thin is still a challenge. In this article, we propose a novel metasurface with negligible thickness as a beam splitter, which can achieve half transmission and half reflection of the incident wave at the same frequency. It also controls the polarization of circularly polarized electromagnetic (EM) waves in the transmission mode. A broadband operation can be achieved based on the geometric phase theory, and the phase control can be achieved by azimuth rotation of the structure. The numerical results of the metasurface are in good agreement with the experimental results in the measured frequency range. The ultrathin multifunctional metasurface realized by the geometric phase principle provides an important stepping stone for simple optical devices and can be extended to a higher frequency range. [ABSTRACT FROM AUTHOR]

The vibration of a planetary gearbox (PG) is complex and mutually modulated, which makes the weak features of incipient fault difficult to detect. To target this problem, a novel method, based on an adaptive order bispectrum slice (AOBS) and the fault characteristics energy ratio (FCER), is proposed. The order bispectrum (OB) method has shown its effectiveness in the feature extraction of bearings and fixed-shaft gearboxes. However, the effectiveness of the PG still needs to be explored. The FCER is developed to sum up the fault information, which is scattered by mutual modulation. In this method, the raw vibration signal is firstly converted to that in the angle domain. Secondly, the characteristic slice of AOBS is extracted. Different from the conventional OB method, the AOBS is extracted by searching for a characteristic carrier frequency adaptively in the sensitive range of signal coupling. Finally, the FCER is summed up and calculated from the fault features that were dispersed in the characteristic slice. Experimental data was processed, using both the AOBS-FCER method, and the method that combines order spectrum analysis with sideband energy ratio (OSA-SER), respectively. Results indicated that the new method is effective in incipient fault feature extraction, compared with the methods of OB and OSA-SER. [ABSTRACT FROM AUTHOR]

The electromagnetic parameter retrieval method based on scattering (S) parameters is widely used because S parameters are easy to obtain. As a classic S parameters retrieval method, the Nicolson–Ross–Weir (NRW) algorithm has problems such as half-wave resonance, phase angle jump, and multivaluedness. In this work, an electromagnetic parameter retrieval method based on deep learning is proposed, which aims to solve the multivaluedness problem in the traditional NRW method. The method we proposed is suitable for retrieval of inhomogeneous medium that satisfies the theory of effective medium. The simulation shows that the electromagnetic parameter retrieval method based on deep learning has high calculation accuracy without the multivaluedness problem. [ABSTRACT FROM AUTHOR]

Sirtuin-3 (SIRT3), the main deacetylase in the mitochondria, maintains cellular energy metabolism and redox balance by deacetylating mitochondrial proteins in a NAD+-dependent manner. Growing evidence indicates that decreased Sirt3 expression is involved in various age-related maladies. However, the role of Sirt3 in ovarian and testicular senescence remains unclear. In this study, we observed that sirt3 expression showed age-dependent decreases in the ovary but not the testis. We generated Sirt3 null mice via CRISPR/Cas9-mediated genome editing. We observed that Sirt3 deletion accelerated ovarian aging, as shown by a decrease in offspring sizes, the follicle reserve and oocytes markers (Bmp15 and Gdf9) as well as increased expression of aging and inflammation-related genes (p16, p21 , Il-1α, and Il-1β). Sirt3 deficiency led to an accumulation of superoxide and disruption of spindle assembly accompanied by mitochondrial dysfunction (uneven mitochondria distribution, decreased mitochondrial potential as well as reduced mitochondrial DNA content) in aging oocytes. Meanwhile, in ovaries of Sirt3 null mice, the impaired mitochondrial functions were shown by decreases in mitochondrial respiratory complexes, along with lower levels of mitochondrial fusion (OPA1, MFN2) and fission (DRP1, FIS1) proteins. er levels of mitochondrial fusion (OPA1, MFN2) and fission (DRP1, FIS1) proteins. Interestingly, Sirt3 −/− male mice exhibited no changes on the testicular histology, serum testosterone levels, germ-cell proliferation, and differentiation of spermatogonia. Meiotic prophase I spermatocytes were also normal. Levels of superoxide, mitochondrial potential as well as expression of mitochondrially-encoded genes were unaltered in Sirt3 −/− testes. Collectively, the results indicated that SIRT3 plays a critical role in maintaining the ovarian follicle reserve and oocyte quality in aging mice, suggesting its important role in controlling ovarian senescence. [Display omitted] • Transcriptional profile of Sirt3 decreased in ovaries but not testes during aging. • Sirt3 deficiency accelerates ovarian aging and impacts oocytes quality. • Sirt3 −/− male mice exhibits normal spermatogenesis. [ABSTRACT FROM AUTHOR]

The use of nitrogen fertilizer is a crucial agronomic practice to increase crop output and quality. This study investigated the impact of five nitrogen application levels (0, 60, 135, 210, and 285 kg N/hm2) on the physicochemical properties of foxtail millet (FM) starch. Optimal nitrogen application (210 kg N/hm2) significantly increased L*, a*, and b* values, water and oil absorption capacity, water solubility, and swelling power of starch. The number of small starch granules increased as the nitrogen application rate increased, but the granule morphology and typical A-type pattern did not change among the treatments. Nitrogen application increased the relative crystallinity and ordered structure, resulting in a higher gelatinization enthalpy. Compared to the control group (7.02 J/g), the enthalpy increased by 21.94 %, 66.38 %, 73.50 %, and 103.28 % under the nitrogen application rates, respectively. Moreover, nitrogen application greatly increased the percentage of A and B3 chains while it lowered the apparent amylose content, peak viscosity, and final viscosity. The effects of 210 and 285 kg N/hm2 treatments on the water solubility and swelling power, water and oil absorption, and light transmission of starch were greater compared to the 60 and 135 kg N/hm2 treatments. These results indicate that nitrogen fertilization significantly affects the physicochemical properties of FM starch. [ABSTRACT FROM AUTHOR]

The use of nitrogen fertilizer is a crucial agronomic practice to increase crop output and quality. This study investigated the impact of five nitrogen application levels (0, 60, 135, 210, and 285 kg N/hm2) on the physicochemical properties of foxtail millet (FM) starch. Optimal nitrogen application (210 kg N/hm2) significantly increased L*, a*, and b* values, water and oil absorption capacity, water solubility, and swelling power of starch. The number of small starch granules increased as the nitrogen application rate increased, but the granule morphology and typical A-type pattern did not change among the treatments. Nitrogen application increased the relative crystallinity and ordered structure, resulting in a higher gelatinization enthalpy. Compared to the control group (7.02 J/g), the enthalpy increased by 21.94 %, 66.38 %, 73.50 %, and 103.28 % under the nitrogen application rates, respectively. Moreover, nitrogen application greatly increased the percentage of A and B3 chains while it lowered the apparent amylose content, peak viscosity, and final viscosity. The effects of 210 and 285 kg N/hm2 treatments on the water solubility and swelling power, water and oil absorption, and light transmission of starch were greater compared to the 60 and 135 kg N/hm2 treatments. These results indicate that nitrogen fertilization significantly affects the physicochemical properties of FM starch. [ABSTRACT FROM AUTHOR]

In this paper, a low-loss toroidal dipole metamaterial composed of four metal split ring resonators is proposed and verified at microwave range. Dual-band Fano resonances could be excited by normal incident electromagnetic waves at 6 GHz and 7.23 GHz. Analysis of the current distribution at the resonance frequency and the scattered power of multipoles shows that both Fano resonances derive from the predominant novel toroidal dipole. The simulation results exhibit that the sensitivity to refractive index of the analyte is 1.56 GHz/RIU and 1.8 GHz/RIU. Meanwhile, the group delay at two Fano peaks can reach to 11.38 ns and 12.85 ns, which means the presented toroidal metamaterial has significant slow light effects. The proposed dual-band toroidal dipole metamaterial may offer a new path for designing ultra-sensitive sensors, filters, modulators, slow light devices, and so on. [ABSTRACT FROM AUTHOR]

This article introduces a wideband pattern reconfigurable antenna made of seawater. A special funnel‐shaped metal structure is used for feeding to increase the bandwidth of the antenna. The antenna‐design refers the electronically steerable parasitic array radiator antenna principle, and arc‐shaped water columns are introduced around the seawater monopole antenna to operate as parasitic passive oscillators. These parasitic elements turn the omnidirectional antenna into a directional antenna. The proposed antenna has more than one mode. When the number of parasitic elements is 2, 3, and 4, it respectively corresponds to three different working modes: dual‐beam radiation, wide‐angle radiation, and directional high‐gain radiation. And in all these three modes, changing the position of the parasitic elements can achieve 360° beam‐sweeping in the 1.66 ~ 2.78 GHz. A prototype is fabricated and verified, and the experimental results are in good agreement with the simulated results. The antenna is filled with seawater when in use, and the weight can be reduced by draining the seawater when not in use. There is great application potential in the field of maritime communications. [ABSTRACT FROM AUTHOR]

Traditional absorbing materials have certain limitations in coping with complex electromagnetic environments. As an area of significant concern in research, water-based metamaterial absorbers are expected to become one of the essential solutions to the current electromagnetic wave pollution problem. This paper uses rubber and a multi-layer water structure to design a metamaterial with high-performance absorption. The simulation results demonstrate that the proposed water-based metamaterials are able to achieve 90% absorption in the frequency band from 11.17 to 25.16 GHz. Specifically, the Ku band’s average absorption rate reaches as high as 99.34%. The absorption characteristics of the water-based metamaterials include polarization insensitivity and wide-angle incidence in both TE and TM modes. Moreover, broadband absorption is achieved even at a large incident angle of the TM mode. The electric and magnetic field distributions indicate that the exceptional absorption of the water-based metamaterial relies primarily on the magnetic resonance generated by the multi-layer water structure. The proposed metamaterial is utilized for multiple-band signal shielding, effectively addressing communication signal interference and electromagnetic leakage from electronic equipment, and safeguarding against electromagnetic interference in practical applications. [ABSTRACT FROM AUTHOR]

A microelectromechanical systems (MEMS) low-g inertial switch is typically used for linearly increased/decreased acceleration signal sensing. In this paper, we introduce a novel design concept of MEMS inertial switch based on direct contact sensing method to eliminate the bouncing effect of the output signal. The switch was designed with a threshold value of 12 g and composed by a proof mass, suspended by six Z-shaped flexure beams. The fabrication was carried out on a silicon-on-insulator (SOI) wafer with standard silicon micromachining. Two glass wafers were used to encapsulate the switch and establish a direct connection between the movable electrode and the detection circuits. According to the centrifugal experiment results, the measured threshold value is around 11.8 g, which is in good agreement with the designed value. The comparison of contact behavior between direct and indirect contact switches was also carried out. The results showed that the direct contact switch could eliminate the output signal bouncing effect, especially when the applied acceleration signal was approximate to the threshold value of the switch. [ABSTRACT FROM AUTHOR]

Highlights • The sensor takes advantage of the coupling between two square rings connected by interdigital capacitor. • Relatively low frequency is achieved with compact dimension. • The sensor realizes relatively high sensitivity and the bandwidth is less than 100 MHz at working frequency of 900 MHz. • Equivalent circuit is given and in well agreement with simulations. • The experimental results are well in agreement with simulated results, too. Abstract In this paper, based on the microstrip metamaterial composed of two coupled square rings, a novel liquid permittivity sensor is designed and fabricated. The sensor takes advantage of the coupling between two square rings connected by an interdigital capacitor. It realizes a relatively high sensitivity, and the bandwidth is less than 100 MHz at a working frequency of 900 MHz. The resonance frequency shifts from 810 MHz to 689.5 MHz when the real part of the sample’s relative permittivity shifts from 1 to 78. The experimental results are in good agreement with simulated results. The designed sensor with compact dimensions and operating frequency paves the way for application to the Internet of Things. [ABSTRACT FROM AUTHOR]

Afforestation results in a wide range of soil resources with carbon (C), nitrogen (N), and phosphorus (P) levels that rarely meet microbial elemental demands. Such stoichiometric imbalances result in the limitation of microbial activity by nutrients, and have consequences for microbial C and nutrient use efficiency and ultimately the fate of soil C. However, how microorganisms cope with stoichiometric imbalances following afforestation and how their responses regulate microbial-driven C emissions remain unclear. We compared sites along a 42 year Robinia pseudoacacia afforestation chronosequence on the Loess Plateau of China, to quantify soil microbial nutrient limitation and explore the mechanisms underlying microbe-mediated C dynamics under conditions of stoichiometric imbalance. Soil available nutrients, potential activities of C-, N-, and P-acquiring enzymes, microbial biomass, microbial community composition and diversity, as well as microbial respiration were measured. Results showed that stoichiometric imbalances increased soil enzymatic activities targeting the mobilization of limiting nutrients at different afforestation stages. Specifically, soil microbial communities were limited by C in farmland, co-limited by N and P at the 10-year site, and became more limited by P as stand age increased. Reductions in stoichiometric imbalance along the afforestation chronosequence corresponded to an increased microbial alpha diversity and fungi-to-bacteria ratio. Stoichiometric imbalances were more strongly associated with changes in soil bacterial beta diversity than fungal beta diversity. Bacterial communities transitioned from being oligotrophic (Actinobacteria dominant) to copiotrophic (Proteobacteria dominant) during forest development, and this was significantly related to stoichiometric imbalance. However, no significant correlation was detected between stoichiometric imbalance and the dominant fungal phyla (i.e., Ascomycota , Basidiomycota , and Zygomycota). The synergistic responses of enzymatic stoichiometry and microbial community properties to stoichiometric imbalance following afforestation led to reduced microbial threshold elemental ratios, which elevated microbial C use efficiency and increased biomass turnover time, further suppressing microbial respiration. Such collaborative-adaptations imply that more C will be diverted into microbial biomass rather than losing, thus could be favorable to soil C storage. Collectively, these findings highlight the importance of stoichiometric imbalances in regulating microbial-driven C emissions and contribute to an improved understanding of how substrate quality changes induced by revegetation influences terrestrial C flows in ecologically fragile areas. Image 1 • Afforestation lowered stoichiometric imbalances and increased soil enzyme activity. • Afforesting farmland deregulated microbial C limitation but increased P limitation. • Soil bacteria was more sensitive to the C:N:P stoichiometric imbalances than fungi. • Forestation reduced microbial threshold elemental ratios, raising C use efficiency. • Increased microbial C use efficiency and biomass turnover time reduced respiration. [ABSTRACT FROM AUTHOR]

Afforestation has been proven to have enormous potential for carbon (C) sequestration; however, the dynamics of aggregate-associated organic carbon (OC) following afforestation and their contribution to changes in bulk soil OC are not well understood in regions with serious soil erosion. Therefore, we investigated the dynamics of OC associated with aggregates along a Robinia pseudoacacia (RP) afforestation chronosequence in the Loess Plateau. Soil aggregate size distribution and OC dynamics in bulk soil were analyzed 10, 18, 28, and 42 years after RP afforestation at depths of 0–20 cm and 20–40 cm. Results showed that total macroaggregates (>0.25 mm), mean weight diameter, and geometric mean diameter increased significantly with stand age, after 42 years of afforestation, increased by 433.5%, 437.2%, 302.1% in the 0–20 cm depth, respectively, while microaggregate amounts decreased by 52.9%, and the proportions of silt + clay fraction showed no obvious changes. Long-term afforestation increased OC content and stock, both in bulk soil (245.6% and 222.9% in the 0–20 cm depth, respectively) and soil aggregates. The improvement of soil structure and enrichment of OC stocks were greater at the 0–20 cm depth than the 20–40 cm depth. In addition, small macroaggregates (2–0.25 mm) contained the highest OC content and microaggregates (<0.025 mm) had the highest OC stocks regardless of soil depth and stand age. Across the afforestation chronosequence, OC content and stock in bulk soil positively correlated with large macroaggregate (>2 mm) amounts and small macroaggregate (2–0.25 mm) associated OC dynamics (P < 0.01). These results indicated that changes in bulk soil OC dynamics mainly depend on changes in the proportion of large macroaggregates and in the OC dynamics associated with small macroaggregates after RP afforestation. • Afforestation resulted in the improvement of soil structure in different layers. • Afforestation increased OC content and stock both in bulk soil and soil aggregates. • The accumulation of OC occurring mainly in microaggregates at both soil depths. • Bulk soil OC dynamics depend largely on changes in large macroaggregate amounts. • Drivers at increase in soil OC stock from small macroaggregates OC content increase. [ABSTRACT FROM AUTHOR]